The gunshot was deafening, Hill writes. "The impact was like the sound of a melon shattering onto cement," he said.

Kennedy held her husband in her arms shouting, "Jack, Jack, what have they done to you?"

She refused to let him go, not wanting people to see him die. "I recognized that the problem was she didn't want anyone to see him," Hill said on the Today show. "It was a gory situation. And so I took my jacket off and I covered his head and upper back. Then she let go."

Hill knew exactly what he had to do. "Somebody had fired a shot at the President, and I had to get myself between the shooter and the President and Mrs. Kennedy," he wrote. "Nothing else mattered."

Hill remembers that, after the shooting, the First Lady cut her husband's hair with a pair of scissors that another secret service agent had brought.

Hill still feels guilt over the shooting, saying that he could have taken the third bullet had he moved sooner. "I had problems sleeping," he said on the Today show. "I had nightmares, I went into a very deep depression, I cut myself off from friends and family."